Add Vulkan to in-progress section of the landing page.
Add Vulkan to in-progress section of the landing page.

Change-Id: Ib1f911d1a30921e4d74d405b77f930754a647d17
Reviewed-on: https://chromium-review.googlesource.com/374048
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

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